Antibacterial Effects of Gold Nanoparticles in Different Shapes With and Without Laser

Abstract Background: Gold nanoparticles (Au-NPs) possess excellent antibacterial properties and are considered an alternative material for treating antibiotic-resistant bacteria due to their unique physical, chemical, and biological properties. Au-NPs and gold nanorods (Au-NRs) have an inhibitory effect on coliform bacteria growth and mitosis. Objectives: To study the effect of Au-NPs (rods, spherical) antibacterial efficiency using with and without laser beam against Escherichia coli . Materials and Methods: Au-NPs and Au-NRs were fabricated by pulsed laser ablation method, where UV-Vis spectroscopy, transmission electron microscopy, and dynamic light scattering investigated the optical and structural properties. The bactericidal effect of these nanoparticles was then assessed with and without exposure to a 532 nm laser, using the counting method (CFU/mL). Results: This effect increases with increasing Au-NP concentration. However, upon exposure to the laser beam, a less significant decrease in the number of bacterial cells was observed compared to the control group. The bactericidal effect of the Au-NPs is enhanced when activated by the 532 nm laser light. Interestingly, the lower concentration of Au-NRs (0.1 mL) had a stronger inhibitory effect on bacteria than the higher concentration (1 mL), possibly due to the accumulation of Au-NR at higher concentrations, which reduces its effective surface area to interact with bacteria and thus reduces its antibacterial activity. Conclusions: The study concluded that the antibacterial effect of Au-NPs and Au-NRs was enhanced when they were exposed to 532 nm laser light. This effect may be due to the high temperature caused by the absorption of laser light and nanoparticles, leading to thermal damage and cell death. The largest decrease in bacterial survival was observed with 1 mL of the photoactivated Au-NRs. However, Au-NR at higher concentrations showed reduced effectiveness due to accumulation, which suggests the need for a balance in concentration for optimum antibacterial effect.